Rajon Rondo knows one thing: “If it doesn’t kill you it will make you stronger,” the Boston Celtics point guard said.

What he might not understand is that his Celtics are killing their fans. The people who watched them roll to their 17th NBA title last season are seeing nothing more than an ordinary team right now, and when you consider that Wednesday’s 89-85 Garden loss to the Houston Rockets was their sixth in eight games, well, that’s a bit less than ordinary, isn’t it?

What’s the problem? What isn’t the problem? Celtics players seem to think it’s defense. Coach Doc Rivers says his club actually played pretty good defense against the Rockets. With Paul Pierce, Kevin Garnett and Ray Allen going 1-for-10 in the fourth quarter, with Rondo limited to five points and five assists one night after turning the ball over nine times, with the Celtics scoring only 54 points over the final three quarters, perhaps he has a case, but some of the accustomed championship defense might go a long way to promoting some easy offense.

Rivers tells his players that it’s going to be like this every night, but they seem to have forgotten.

They all know that these are the dog days of the NBA season, but what team doesn’t have to deal with that? The Celtics did last season. After winning 19 straight games, the Celtics have gone sour, and a loss on their home court to a team that was without Tracy McGrady and Shane Battier, and a team that lost Ron Artest to fouls down the stretch was like sucking a lemon sprinkled with sour milk.

Over the last couple of weeks the Celtics have been outscored by the Lakers, 12-3, down the stretch. They were outscored by the Warriors, 35-17, in the fourth quarter and they blew a 23-13 first-quarter lead to a Blazers team that didn’t have Brandon Roy. And Tuesday night at Charlotte? Outscored, 17-9, in overtime. Rivers didn’t even want to talk about that.

One thing the Celtics do talk about, though, is confidence and togetherness. If nothing else, they’ve got it.

“I think the confidence is still there,” said Pierce, who tied Houston’s Yao Ming for scoring honors with 26 points. “It’s a long season, and that’s what we try to tell each other. We bend but we don’t break, and that’s what it’s all about. We preach the word Ubuntu and what it means through difficult times. We stay together. Nobody’s pointing the finger. It’s a tough stretch, but we know what we’re capable of.”

Yeah, it is a tough stretch. The Celtics have played 37 games, 17 on the road, but had played six of seven on the road since Christmas Day when the 19-game winning streak ended in LA. Rivers notes that the team has been home for about three days since Dec. 23. He calls this the toughest stretch of the season.

Page 2 of 2 - Is that an excuse, though?

“I think it’s more mental than anything,” said Garnett, who had 18 points and eight rebounds. “I think when he said that he meant mentally tough. We’ve had two real difficult months, but we’ve weathered the storm. As of late we have had some slippage in the defense and it goes to show you what practice time (means) and the things you can clean up in practice, which we haven’t had a lot of.”

That said, Rivers is giving his team Thursday off, sort of a mental health day. He said he can accomplish a lot at a shootaround in Cleveland Friday. Yes, Cleveland, home of the NBA-leading Cavaliers. “We’re gonna watch film,” said Garnett. “Then we’ll conversate and try to get ready for Cleveland.”

“Conversating” is one thing, but if there’s one thing that’s going for this team, at least, it’s that the players are together, solidly behind one another.

“Everyone is heading in the right direction,” said Glen Davis, who did a nice job on Yao in the third quarter.

“We just have to get a piece here, a piece there to make sure we finish the deal. You can win a lot of games, but you can also lose a lot games. The characteristic of a champion is to fight back.”

“We’ve got to get our defensive swagger back,” Pierce said. “It’s been broken the last 10 or 12 days. We know what we’re capable of. It’s just about going back to the basics and doing what we do.”